One of the most evolved and intelligent of fishes, all possess an electrical system used to at the very least serve as an addition sense. All are on different frequencies so the possibility exists they communication with some sort of fish wifi.

If you were intelligent and had something like this how cold you not use it for at least some soft of communication? This might explain the different frequencies?

In several places around the world fish have evolved cit off from all light for a very long time. Although not necessarily related to each other there are grouped here instead out of ichthyological curiosity.